During solar storms, the Sun expels large amounts of energetic particles (SEP) that can react with the Earth's atmospheric constituents and produce cosmogenic radionuclides such as
C,
Be and
Cl. Here ...we present
Be and
Cl data measured in ice cores from Greenland and Antarctica. The data consistently show one of the largest
Be and
Cl production peaks detected so far, most likely produced by an extreme SEP event that hit Earth 9125 years BP (before present, i.e., before 1950 CE), i.e., 7176 BCE. Using the
Cl/
Be ratio, we demonstrate that this event was characterized by a very hard energy spectrum and was possibly up to two orders of magnitude larger than any SEP event during the instrumental period. Furthermore, we provide
Be-based evidence that, contrary to expectations, the SEP event occurred near a solar minimum.
Understanding the temporal variation of cosmic radiation and solar activity during the Holocene is essential for studies of the solar-terrestrial relationship. Cosmic-ray produced radionuclides, such ...as 10Be and 14C which are stored in polar ice cores and tree rings, offer the unique opportunity to reconstruct the history of cosmic radiation and solar activity over many millennia. Although records from different archives basically agree, they also show some deviations during certain periods. So far most reconstructions were based on only one single radionuclide record, which makes detection and correction of these deviations impossible. Here we combine different 10Be ice core records from Greenland and Antarctica with the global 14C tree ring record using principal component analysis. This approach is only possible due to a new high-resolution 10Be record from Dronning Maud Land obtained within the European Project for Ice Coring in Antarctica in Antarctica. The new cosmic radiation record enables us to derive total solar irradiance, which is then used as a proxy of solar activity to identify the solar imprint in an Asian climate record. Though generally the agreement between solar forcing and Asian climate is good, there are also periods without any coherence, pointing to other forcings like volcanoes and greenhouse gases and their corresponding feedbacks. The newly derived records have the potential to improve our understanding of the solar dynamics and to quantify the solar influence on climate.
In the Alps, climatic conditions reflected in glacier and rock glacier activity in the earliest Holocene show a strong affinity to conditions in the latest Pleistocene (Younger Dryas). Glacier ...advances in the Alps related to Younger Dryas cooling led to the deposition of Egesen stadial moraines. Egesen stadial moraines can be divided into three or in some cases even more phases (sub-stadials). Moraines of the earliest and most extended advance, the Egesen maximum, stabilized at 12.2
±
1.0
ka based on
10Be exposure dating at the Schönferwall (Tyrol, Austria) and the Julier Pass-outer moraine (Switzerland). Final stabilization of moraines at the end of the Egesen stadial was at 11.3
±
0.9
ka as shown by
10Be data from four sites across the Alps. From west to east the sites are Piano del Praiet (northwestern Italy), Grosser Aletschgletscher (central Switzerland), Julier Pass-inner moraine (eastern Switzerland), and Val Viola (northeastern Italy). There is excellent agreement of the
10Be ages from the four sites. In the earliest Holocene, glaciers in the northernmost mountain ranges advanced at around 10.8
±
1.1
ka as shown by
10Be data from the Kartell site (northern Tyrol, Austria). In more sheltered, drier regions rock glacier activity dominated as shown, for example, at Julier Pass and Larstig valley (Tyrol, Austria). New
10Be dates presented here for two rock glaciers in Larstig valley indicate final stabilization no later than 10.5
±
0.8
ka. Based on this data, we conclude the earliest Holocene (between 11.6 and about 10.5
ka) was still strongly affected by the cold climatic conditions of the Younger Dryas and the Preboreal oscillation, with the intervening warming phase having had the effect of rapid downwasting of Egesen glaciers. At or slightly before 10.5
ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate. Between about 10.5
ka and 3.3
ka conditions in the Alps were not conducive to significant glacier expansion except possibly during rare brief intervals. Past tree-line data from Kaunertal (Tyrol, Austria) in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the Swiss and Austrian Alps points to long periods during the Holocene when glaciers were smaller than they were during the late 20th century. Equilibrium line altitudes (ELA) were about 200
m higher than they are today and about 300
m higher in comparison to Little Ice Age (LIA) ELAs. The Larstig rock glacier site we dated with
10Be is the type area for a postulated mid-Holocene cold period called the Larstig oscillation (presumed age about 7.0
ka). Our data point to final stabilization of those rock glaciers in the earliest Holocene and not in the middle Holocene. The combined data indicate there was no time window in the middle Holocene long enough for rock glaciers of the size and at the elevation of the Larstig site to have formed. During the short infrequent cold oscillations between 10.5 and 3.3
ka small glaciers (less than several km
2) may have advanced to close to their LIA dimensions. Overall, the cold periods were just too short for large glaciers to advance. After 3.3
ka, climate conditions became generally colder and warm periods were brief and less frequent. Large glaciers (for example Grosser Aletschgletscher) advanced markedly at 3.0–2.6
ka, around 600 AD and during the LIA. Glaciers in the Alps attained their LIA maximum extents in the 14th, 17th, and 19th centuries, with most reaching their greatest LIA extent in the final 1850/1860 AD advance.
Trace-level plutonium in the environment often comprises local and global contributions, and is usually anthropogenic in origin. Here, we report estimates of local and global contributions to ...trace-level plutonium in soil from a former, fast-breeder reactor site. The measured
Pu/
Pu ratio is anomalously low, as per the reduced
Pu yield expected in plutonium bred with fast neutrons. Anomalies in plutonium concentration and isotopic ratio suggest forensic insight into specific activities on site, such as clean-up or structural change. Local and global
Pu contributions on-site are estimated at (34 ± 1)% and (66 ± 3)%, respectively, with mass concentrations of (183 ± 6) fg g
and (362 ± 13) fg g
. The latter is consistent with levels at undisturbed and distant sites, (384 ± 44) fg g
, where no local contribution is expected. The
Pu/
Pu ratio for site-derived material is estimated at 0.05 ± 0.04. Our study demonstrates the multi-faceted potential of trace plutonium assay to inform clean-up strategies of fast breeder legacies.
The functionality and retention capacity of water reservoirs is generally impaired by upstream erosion and reservoir sedimentation, making a reliable assessment of erosion indispensable to estimate ...reservoir lifetimes. Widely used river gauging methods may underestimate sediment yield, because they do not record rare, high‐magnitude events and may underestimate bed load transport. Hence, reservoir lifetimes calculated from short‐term erosion rates should be regarded as maximum values. We propose that erosion rates from cosmogenic 10Be, which commonly integrate over hundreds to thousands of years, are useful to complement short‐term sediment yield estimates and should be employed to estimate minimum reservoir lifetimes. Here we present 10Be erosion rates for the drainage basins of six water reservoirs in Western Turkey, which are located in a tectonically active region with easily erodible bedrock. Our 10Be erosion rates for these catchments are high, ranging from ∼170 to ∼1,040 t/km2/yr. When linked to reservoir volumes, they yield minimum reservoir lifetimes between 25 ± 5 and 1,650 ± 360 years until complete filling, with four reservoirs having minimum lifespans of ≤110 years. In a neighboring region with more resistant bedrock and less tectonic activity, we obtain much lower catchment‐wide 10Be erosion rates of ∼33 to ∼95 t/km2/yr, illustrating that differences in lithology and tectonic boundary conditions can cause substantial variations in erosion even at a spatial scale of only ∼50 km. In conclusion, we suggest that both short‐term sediment yield estimates and 10Be erosion rates should be employed to predict the lifetimes of reservoirs.
Key Points
Cosmogenic nuclide‐based erosion rates for catchments in Western Turkey range from ∼13 to ∼417 mm/kyr (or ∼33 to ∼1,040 t/km2/yr)
(10)Be erosion rates for the drainage areas of six water reservoirs yield minimum reservoir lifetimes between 25 ± 5 and 1,650 ± 360 years
Estimation of reservoir lifetimes should be based on both short‐term sediment yield estimates and catchment‐wide (10)Be erosion rates
Recently, it has been confirmed that extreme solar proton events can lead to significantly increased atmospheric production rates of cosmogenic radionuclides. Evidence of such events is recorded in ...annually resolved natural archives, such as tree rings carbon-14 (14C) and ice cores beryllium-10 (10Be), chlorine-36 (36Cl). Here, we show evidence for an extreme solar event around 2,610 years B.P. (∼660 BC) based on high-resolution 10Be data from two Greenland ice cores. Our conclusions are supported by modeled 14C production rates for the same period. Using existing 36Cl ice core data in conjunction with 10Be, we further show that this solar event was characterized by a very hard energy spectrum. These results indicate that the 2,610-years B.P. event was an order of magnitude stronger than any solar event recorded during the instrumental period and comparable with the solar proton event of AD 774/775, the largest solar event known to date. The results illustrate the importance of multiple ice core radionuclide measurements for the reliable identification of short-term production rate increases and the assessment of their origins.
We constrain the Holocene development of the active Bleis
Marscha rock glacier (Err–Julier area, eastern Swiss Alps) with 15
cosmogenic nuclide exposure ages (10Be, 36Cl), horizontal surface
creep ...rate quantification by correlating two orthophotos from 2003 and 2012,
and finite element modeling. We used the latter to separate the control on
surface movement exerted by topography and material properties. Bleis
Marscha is a stack of three overriding lobes whose formation phases are
separated by time gaps expressed morphologically as over-steepened terrain
steps and kinematically as a sharp downslope decrease in surface movement. The
three discrete formation phases appear to be correlated to major Holocene
climate shifts: Early Holocene low-elevation lobes (∼8.9–8.0 ka, after the Younger Dryas), Middle Holocene lobe (∼5.2–4.8 ka, after the Middle Holocene warm period), and Late Holocene
high-elevation lobes (active since ∼2.8 ka, intermittently
coexisting with oscillating Bleis Marscha cirque glacierets). The formation
phases appear to be controlled in the source area by the climate-sensitive
accumulation of an ice-debris mixture in proportions susceptible to rock
glacier creep. The ongoing cohesive movement of the older generations requires
ice at a depth which is possibly as old as its Early–Middle Holocene debris
mantle. Permafrost degradation is attenuated by “thermal filtering” of the
coarse debris boulder mantle and implies that the dynamics of the Bleis
Marscha lobes that once formed persisted over millennia are less sensitive
to climate. The cosmogenic radionuclide inventories of boulders on a moving
rock glacier ideally record time since deposition on the rock glacier root
but are stochastically altered by boulder instabilities and erosional
processes. This work contributes to deciphering the long-term development
and the past to quasi-present climate sensitivity of rock glaciers.
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